don't know if this helps, but I have a couple of spiceworks setup at a couple of remote sites with my main site setup as the central server. Whenever the connection goes down between one of my remote sites and the central server I get notified. Maybe you could try setting something like this up to monitor and document via email when your connection goes down.

If you don't have multiple sites, you could set up a simple web server and use a service like Chartbeat (there's a 30 day trial, then $10/month). They will monitor your site and notify you of a downtime. Then, you can easily track when your "site" has gone down.

Check out PRTG (http://www.paessler.com/prtg/). It's easy to setup and use, and makes historical logs and charts, which you can demonstrate to your boss to give hard technical evidence, not just anecdotal evidence.

Install PRTG inside your network, then set it up to monitor a few highly-reliable external resources. Perhaps a PING test to a major internet router, and also perhaps an HTTP query to a major internet website. Essentially try to monitor 2-3 different sources that are all extremely unlikely to ever go offline.

Compare the PRTG monitor graphs for all 3 external targets. If one of them goes down, but the others don't, then it was probably a problem on their end. If all three of them go down at the same time, then it was almost certainly a problem on your end (bad DSL).

You can also go another step further, and setup ANOTHER second PRTG outside your company, like at your home or a remote office, and have it do an SNMP monitor of your office DSL router's WAN interface from outside (across the internet). If your DSL or router goes down, the remote PRTG will show a confirmational outage.

If your DSL goes down, now both your internal (looking out to the internet) and external (looking in from the internet) PRTG installations should show matching historical "outages" in their logs at the exact same time.

50 bucks if you can guess which service drops on me several times a day...

I had to rewrite a new one, because unlike cable, this service doesn't go "down"...the router intercepts all traffic with a local error page, providing a 1ms ping response. So I had trace-route check for this sort of ultra-fast response.